I understand the cost of skill-level purchase at creation, but how does the cost work, post-creation?

Is it:

A) +5 = (1+2+4+8+15) points (total 30 points)? or

B) +5 = 15 points?

ie: Can you save up 15 points and buy a level 5 skill? Or must you purchase each level of the skill?

(On a semi-related note: is the 'Test Character Creation' tool broken? Or am I doing something wrong? It used to be accessible from our character sheet, but now clicking the link just brings up a line of red text.)